The present disclosure relates generally to traffic distribution for wireless clients in a wired network.
When wireless local area networks (WLANs) are deployed, a contiguous radio frequency (RF) region is created due to RF coverage overlapping from different access points (APs). A contiguous RF region may range from as small as a single AP to as large as thousands or even tens of thousands of APs. When a client moves from one AP to another AP it is referred to as client roaming. Roaming within an IEEE 802.11 based WLAN is typically seamless (e.g., client retains existing services and its identity). The demand for fast and seamless roaming with minimal disruption is becoming increasingly important as VoIP phones and dual-mode mobile phones (Cellular+WLAN VoIP) are gaining popularity.
The time period for roaming from one AP to another AP comprises three phases. In the first phase the client searches for a new AP. While the client is scanning different frequency bands searching for surrounding APs to roam to, it tries to maintain a data path connection with the exiting AP so that there is no data path disruption. In the next phase, the client re-associates and re-authenticates to the new AP and its associated switch in a wired network. In this phase the client's policies and context are also transferred to the new switch, depending on the policies configured and the client context the transfer of the context may be a relatively time consuming task which may involve programming the new switch's hardware. The network path then converges to the new AP and switch in the third phase. This third phase is straight forward if roaming is between two APs connected to the same switch (intra-switch roaming). However, when roaming occurs between two APs connected to two different switches, the time required for a network to converge may result in a loss of traffic and degradation in voice call quality. This is due in part to route updates which propagate hop by hop and have to be processed on a switch CPU (central processing unit). Processing times can vary depending on the load on the CPU and other factors. If there is even a small loss of voice traffic during roaming (e.g., over 125 ms), users may perceive a significant drop in voice QoE (Quality of Experience).
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